Just got a new 545 mark II and had lots of fun. I started out using 20LPX with and 18" and was surprised. I didn't expect it to cut so fast. I asked the dealer if it would keep up with my 50cc 346xp (that has been pretty much babied). He said it would be close and he wasn't wrong. I have never ran an AT saw or an earlier 550, 545 etc. so I cannot compare. As far as weight goes, it is heavier than the 346xp but it balances well. I've ran almost 4 tanks through it but not a lot of limbing. Bucking firewood it wasn't much behind my non-cat 359. I was also surprised by Oregon BPX. My dealer said he used a lot of semi-chisel so I ran it a lot today. It seemed like it wasn't as much of a difference in cutting speed compare to using 3/8 chisel vs 3/8 semi chisel. Has anyone else noticed this?