Download the demo to test if you can run it. The graphics are highly customizable and you should be able to get it to run.
Considering the ever growing community, I'd say that it is awesome. It is worth it considering the [endless] amount of replay value.
There are laggy situations, but you can just move to another server(with a lower ping) or host your own(no lag yay). The server can and will crash, but not usually unless you are dealing with dangerous stuff(i.e new mods). I'm not sure about pauses, but if process-heavy actions are taken, you will experience delay.
By process-heavy action, I mean, more or less, spam. This can be resolved by an admin and live may return to normal.
So, download the demo. If you can run it moderately, you should be okay. Fool around with the graphical and advanced options until it runs smoothly. If you are sure you can run it well enough to enjoy it, then I'd say buy it. If not, look into getting a new computer/laptop.
Also, the demo only allows 150 bricks, while the full game allows 128,000(more if you glitch, but can cause crashes).
This is more than enough for almost anything. I've made large DMs in 1,000 bricks or less. If I used the entire limit, it would take hours to walk from end to end.
As another note, the amount of bricks can adversely effect the FPS, but turning down draw distance resolves this quickly.
