Should I buy this game?

Only if you thought MoO2 lacked features and want something more complex.
Seriously MoO2 is like a limited demo for SE: IV Deluxe. After getting used to all the things I can do in SE: IV Deluxe I get bored quickly when playing MoO games. They just seem so limited.

Oh and I'm probably not the best person to answer your question since I think everyone should buy and more importantly play SE: IV Deluxe. :)

Please do. This game can be an enormous time sink and if you like the genre you'll probably get strongly affected by the "One more turn" syndrome. :)

I'd say the game is bigger than MOO2, it has more features, but it's less "well rounded", less "finished". It definitely scratches the same itch, though, so you should enjoy it :)

My history: I bought MOO3 for like $10 a few months after it released. Was too young to realize it was that cheap because no one wanted to buy it. Regardless, I loved the ship battles and played it to the extent that a 10yr old mind could. That was my primer into 4x space strats. I know, I had the equivalent of a crash course from hell.

Anyway after several years I ran into Space Empires 4 after some random internet searching. SE5 was released a year after I found SE4. I love both of those games to death. I tried numerous other space 4x's and none stack up to SE4+SE5. SE4 is the golden standard this whole genre should be measured against. So yes, I say buy it. Luckily, SE4 even works on Win764-bit for me in 1080p resolution. SE5 I can only get to work on my XP machine, it runs slow as molasses on any newer OS's.

It runs well on my Vista Laptop. But not on my win7 desktop : too many graphic glitches, it kills my eyes.

Yeah SE5 is just plain weird on which OS to run on. As I said I still have me mid-2000's XP gaming rig working so I do play it on that when I want. But if I was stuck only with my current Win7 machine I'd not be happy about the incompatibility.