I have a Beam/devices blaster which I really enjoy playing, though it is only at the mid 20s at the moment. I think the question is how do you wantto play? Solo, team, both?
I find that beam/dev is great for solo play, it is mainly single target attacks, but they hit hard. I play it almost like a ranged stalker, which post 20 is easy to do with Field Operative and a celerity steath IO in sprint. (I use it in sprint, even though I am generally hovering, so I can slot something else in hover, it gives a bit more flexibility and can be turned off if the end drain is too much). The combo also works well in small teams, however in big teams the single target attacks, unless it is against hard targets, tends to get a bit lost where your targets usually end up dead before the animation has completed.
In short, if you are wanting to play on big teams I would suggest going either AR or DP as both have much better AoE options.