just copy your existing folder first (all MAME files are stored in the MAME folders unless you specifically tell it otherwise)
some video options did change recently, so you might have to create a new .ini
Some romsets might have changed.
Easiest thing to do is keep both builds handy in their own folders, 0.154 is quite old now (and did have some bugs with Carnevil which might not be to your liking if you're playing gun games) but 0.155 isn't ready.