I've used deca in my last and only two cycles and got some really good results from it. The first time I used deca I used about 250mg/week for 8 weeks and gained about 10 solid lean pounds of muscle. I had a pretty good diet and did a lot of cardio. The second cycle I mixed d-bol and deca (d-bol 25mg/day for 6 weeks & deca 500mg/week for 14 weeks). My strength and size increased a lot, went from 190 to 225 lbs. The only drawback was that I had a problem with water retention and I couldn't seem to control it very well. I think I had some bad reactions to the d-bol, since I couldn't do a lot of cardio because of the muscle cramps and stiffness it gave me. But after I was off the d-bol, things seemed to get better and I continued to gain some really good muscle gains with the deca. I really like deca and I started using it because it's considered one of the safer substances. Plus it's really good on your joints because it lubricates them. Of course after the cycle you might have some joint problems because of the lubrication deficiency, but deca can be used to combat other "joint drying" substances such as winny while on a cycle., so it has its pros and cons. I was always recommended to use it together with test because deca by itself can really shut your hpta down, and you will struggle during your PCT, but it wasn't too bad for me. My libido didn't go down too much and my gains were pretty much stable. But its highly recommended to use together with test. Like many say, test should be the base to all your cycles.
G