Speakin of flattops, the bushmaster super varminter and predator are both nice rifles. DPMS makes a real accurate flat top in 308 that is a great shooter, I am unsure though about its reliability as I have only shot one for a two sessions.
When it comes to assault rifles I tend to think of them in 2 classes.
Assault rifles- M16/AR15 and the AK's like the AK47,AK74, Valmet etc. Basically the light 5.56mm and medium 7.62x39.
Battle rifles- The FN/FAL, HK91,M14/M1A
Now there is a new class developing, such as the AR series of rifles in 6.8 etc. Bridges the gap somewhat.
I am not really in either camp as to which is best for all people/ all uses as their is a place for both types as well as the subgun, tactical shotgun and sniper rifle. However for myself I tend to favor the Battle rifles. I do won and shoot AR's and like them alot. However if you are hunting deer SIZED game, I think commonsense tells us that we need a cartridge up to the job.
I really like the new FN SCAR, however it may be some time, if ever a semi auto civilian version will be available. I'll take mine in 308, thank you very much.
While on cartridges, I think the search for a new cartridge is stupid. The 223 is too light, the 308 too heavy ( in the opinion of some). So they try to create stuff like the 6.8. Well the problem with that cartridge is max effective range, too short.
A .243 with a 100 gr would be ideal. Put it in a M16/AR15 config, change the gas system to a piston, and you would be well equipped.
Which is why I like the new FN SCAR. Basically they took all the good features from the current crop of assault/battle rifles, threw out the bad, used the new manufacturing techniques and materials available, and built what appears to be one HECK of a rifle.