Every preamp I owned previous to my Roadster had an effects loop that was always engaged. I didn't overdo effects, but I did enjoy putting a little chorus and/or delay in the loop for solos and some clean stuff. Never really liked using effects for distorted rhythm. So one day I'm messing with my Roadster, and I decided to turn off the effects loop. I was floored by the clean tones I was getting. Went to the distorted side of things and was amazed by how much better the tone was. Ended up selling my pedals and leaving the effects to the mixing people. The increase in tonal complexity and dynamics made me forget about effects. Plus, I didn't want the effects squashing my tone.
Now I own a TA-15, which doesn't even have an effects loop. I don't miss an effects loop. In fact, my next amp will either not have an effects loop or have a bypass switch! Oh, the Roadster is a great amp, btw, but it's just not me.