I have found mtx to reduce my joint pain quite a bit. Energy is hit and miss, but I do think I've generally felt a LOT better since being on it. I have been on it for about a year and a half now. I started off working my way up to 10 mg/week and I am currently on 15 mg/week. I had some issues with a previous rheumy thinking my low white blood cell count was due to bone marrow suppression from the mtx, so he wanted to take me off of it. My newer rheumy (who I've been seeing for almost a year) recognized that my blood counts are often low in response to disease activity, so he upped my dosage and I've been doing well with that.
I think it took about 3 months for the mtx to fully kick in. I'm not sure that the mtx is responsible for reducing my flares...I tend to think that is more the plaquenil, but I don't really know. I certainly FEEL better with the mtx. As for side effects, I have had occasional nausea when I'm bumping up my dose. I also started getting mouth ulcers constantly, so I take Leucovorin 12 hours after my mtx dose and it counteracts that whole thing. No more mouth ulcers. I always make sure to eat well when I take the mtx and I like to think this helps prevent some side effects.