Format SD card before new ROM?

[Guest Konstipated Kiwi]

I tried a range of different ROMs when I owned my Blade and followed many threads relating to them. I have started doing likewise with my G300. I am interested in the inconsistencies between the experience of different users with any given ROM (some feel the product runs 'flawlessly' while others report lag, force closes, graphical glitches and various other issues). I know some of it will be down to user expectations (what is 'butter smooth' to one may be laggy to to others), some will be down to the specific combination of apps individuals have installed, and some will be down to the specific settings some people use. I am also aware that it is advisable to perform a full range of wipes in CWM before installing a new ROM.

What I want to ask about is whether it is advisable to wipe and format the SD card before changing ROMS as well, to be absolutely sure. The reason I ask is because I have noticed all sorts of detritus on my SD card during my time using smartphones (e.g. directories created by apps, all sorts of guff created during 'supercharging'). On occasions when I tried new ROMS with my Blade I found evidence of settings in a brand new ROM installation that could only have been there because there was legacy from the previous ROM (e.g. personal settings/customisations that I had not restored because I had not even used a restore programme like Titanium Backup; preferring to download the vanilla app from the Market). Further investigation appeared to suggest that the new ROM was retrieving guff from my SD card that had been left by the old ROM; I had formatted one partition but not the other.

Is it possible that directories and files left on an SD card by a previous ROM can cause issues with a new ROM installation? My technical knowledge of how these things work isn't sufficient to be sure.

For my own peace of mind, I always wipe/format everything (where feasible; obviously this approach is only possible when using CWM rather than the official update routes) including the SD card so that my installation is as close to factory (for want of a better word) as possible. I know it is tedious installing all your apps and setting everything up again, but I still find it less frustrating than spending weeks trying to figure out why my ROM isn't working as expected.