No, it's not enough RAM. Think of like like a Windows computer. It can run on 1 gig as the minimum, but runs far smoother on 2gigs. So will the phone run, yes. Can you open up apps, yes, however the problems begin when switching between applications. Your in Twitter for example and the phone rings. You will see a slow reaction. You may hear it ring but can't answer at first. Or you screen shot something, then press share to bring up apps used to share things. Again, you will get a slow reply or response. It does catch up but it takes a while ad it becomes annoying.
1 GIG works, but I would suggest you treat that a the lowest.
1.5 is perfect, if you can find it. I had the HTCDesire 816. 1.5 Gig of ram, worked great.
2.gigs puts you in the sweet spot, as you will know you can handle anything, any new app out there for a while to come.
One more thing. Free App, Android Assistant. You can set it to Free up your Cache and RAM every 3 hours or so. This will help too, free up the memory for you.