If I had to compare CD to opera for memory use. I would it's not bad.
(Although like CD, opera is still being worked on) I'm also guessing it depend on your computer configurations too and how many tabs you have opened.
Like windows XP, Vista, 7 (32 or 64 bit) How much memory your computer has (128mb, 256, 512, 1GB 2GB 4GB etc, etc.
These were some result for "opera 10.50"
I don't know, hwat problem you have on your W7, but in XP, in my case, with 17 tabs opened, Opera beta eat 299,435 K/RAM. Same version, but on poorer configuration, with only 512 MB/RAM PC, it uses with 17 tabs opened, just 190,233K/RAM. Maybe is something wrong with your OS. Who knows?
W7 x64, 15 tabs opened - 281,656MB ram used, which i dont care, 4gb in total so I never use more than 50% until play games. But i guess opera has a dynamic core which will use more or less ram depending on your system settings like page file size, how often you visit site (precashing on you hard drive) and ram amount. But it is only a guess

. The only problem I am facing using opera is that it lack support for Ai Roboform!! - I am not talking about that rubbish web applet . Who knows.. maybe one day

Thanks on update! This new final Opera version looks very good on Win7.
Thekid1,
I agree with you. Opera uses about 280MB of ram on my system. I think it`s because of the native AERO interface.