I think transaction fees currently make BTC non-viable as an actual currency, but it still has value as an investment. I'm not holding a lot, but I'm currently buying £50-100/month as a disposable income/see what happens play.
Basically each month I increase my holding to the next £100 level - so if I start March at £300 and my holding are worth £340 by the beginning of April, I buy another £60 to take it to £400. Doing it that way helps me keep an eye on growth, because I can see the amount I need to invest grow or shrink according to the coin growth. That means I can do some basic level of growth tracking through my normal accounting processes.