Essentially what Solid Hits does is make you hit more line drives on squared up pitches instead of popups or lazy flys, so it will increase HRs, but it will also make your batting average go up a bit. For me, this is ideal because, after the patch, I was seeing a lot of balls that should be smoked just end up as weak outs, so I was seeing less extra base hits in general...so this did the trick, in addition to increasing Power + 1.