Seen those vids, but thanks anyway.

Well 5+ months after my initial assessment I'm fairly disappointed with the game. Granted I've gotten about sixty hours out of it but it still has a lot of flaws mostly stemming from Gearbox half-assing things. The game could have been so much more than what it is but ultimately it has just turned into a scam to bilk people via DLC. Haven't played any of the DLC but from what I hear the first two aren't that great (and both have SecuRom) while the third is fairly solid. Still, I haven't even finished the main quest due to disinterest so I won't be picking up the DLC unless I find it on sale for under five bucks.
If you can find it for $20 or so it's probably worth it. If you can get a couple of friends to play it with you then its a lot better.

As I said, once done it's done. Can't play anymore. DLC just adds a few more hours of pure fun before you get there and not worth the money. I played with 2 other guys beginning to end so I liked it a lot that one time through, you probably played alone plenty and that would leave me sour for sure.
At $20 this game is great. I would get the DLC if they were $5 new when they came out, but even if they hit $5 now I wouldn't get them. I already played the game until it's dead.

From the sound of it, you weren't a huge fan of Diablo 2. If that is the case, it is to be expected that you found Borderlands to be a major disappointment.
I've played countless hours of Diablo 2, so it is the standard by which I measure Borderlands. There are a few key areas where Borderlands disappointed me.
1. Sparse skill trees and a single special ability. Some of Diablo 2's greatest strengths were its skill trees and abilities. They were easy to understand, yet offered a great variety of choices. Each character had at least 2 or 3 tried and true cookie cutter builds and any number of customized variants. With Borderlands, each character has essentially one build with slight variations. Lack of variation and customization in skill trees is a very real reason to only play the game a few times.
2. Lack of customizable items. In addition to rare, unique, and magic items, Diablo's socketed, runeword, and crafted items added an extra level of customization. The necessity to collect not only weapons, but also armor, rings, amulets, and charms increased the desire to spend endless hours hunting for loot. The sheer number of guns in Borderlands is nice, but there is no way to create custom items. One little character mod hardly makes up for all of the various items Diablo 2 offered.
3. Low level cap. Diablo 2's level cap of 99 was so high that it couldn't be reached without excessive playing above and beyond a single play through all 3 tiers of the story mode. It gave players a reason to continue to improve their characters after completing the story. The level cap in Borderlands is too low to encourage high level characters to continue playing.
At the end of the day, at its core Borderlands feels like a new version of Diablo 2 that has been dumbed down for the console market. All that said, the game can still be a lot of fun to play with friends. If you don't intend to play it cooperatively with friends, you won't get much out of it.

Yeah I played a few times with friends but not much since we'd play at different times and the questing system was a bit borked when it came to cooperative play. And I definitely agree that the talent system was extremely disappointing. As I said: they had the groundwork for something really good but just didn't follow it through.

I'm hoping $DLC #3 (General Knoxx) comes to disc soon and that a $DLC4 gets announced and released soon - and of course put on disc.
I'd love to see a DLC $3 and #4 combo pack on DVD - like they did w/ DLC 1 and 2.
I really liked Zombie Island $DLC. :)

I have Knoxx on Steam and finished it, it is really worth it. But I am waiting for a deal for first two DLC. I hope they will make a Steam deal.

I stopped playing after a while (can't remember how far I got, maybe level 30). Mostly, I just got tired of fighting the same enemies against the same scenery over and over.
I found the hype over the variety of guns to be rather overblown. Much is made of all the strange and cartoonish guns you find lying around, but I never really found anything more exotic than extra lightning damage, save for a few static quest rewards like the shotgun that fires an incredibly useless energy wave.
For the most part, different weapons are just a few standardized variations on a theme; this shotgun fires seven pellets, whereas this other shotgun fires six pellets in a slightly narrower spread. It didn't take me long to find the manufacturers and stat templates that I liked, and when upgrading my gear, I just stuck with weapons that fit my preferred blueprints.