If you set up an encrypted LVM, you will have essentially the same method of encryption that TrueCrypt offers. TC also has some added extras like hidden operating systems and volumes, which are useful for situations in which plausible deniability is required (for example, if a kidnapper is forcing you to give them your password). There is a minimal performance hit when using an encrypted LVM, but I've never even noticed it on any reasonably-powered laptop.
In Ubuntu (post-Karmic, I think), there is also an option to encrypt a user's files transparently. So if you login as that user, you can access your files normally, but if not they are encrypted. This model has some advantages over full-disk or LVM encryption, but also some disadvantages. One advantage is that you can have one machine with multiple users and each can decrypt and view only their own files (by contrast, once an LVM is decrypted any user can view the entire disk). It can also be helpful if you mess up some part of your system and can't boot normally, since you can boot from a LiveCD and access the system files to repair them easily (by contrast, you'd need to decrypt and mount your LVM to fix a system crash, which is doable but not trivial). A disadvantage of user home directory encryption is that files outside of that directory are not encrypted, and information can easily "leak" out into other parts of the drive if you're not careful (although at least in Ubunu Lucid, I believe the swap partition is also encrypted by default).
I would never have a laptop without encryption nowadays. My data is worth much more to me than my hardware. Even if a thief were uninterested in my data, the time it would take me to change all of my access info and other sensitive data if it were stolen would be a major loss to me.
Personally I haven't decided which method I prefer (LVM or home directory encryption). I am the only user on my machines, and LVM "feels" safer to me because I know that everything on the drive will always be encrypted. But I've used home directory encryption on my last two Ubuntu installations on my main laptop, and twice now I've had to edit system files from a USB boot disk in order to fix some startup issue, and I was very glad I wasn't using LVM then (the second time I was waiting for a flight in an airport when I borked my system, and I never would've been able to recover it and work on the plane if I'd had LVM encryption).
A BIOS password is only useful if the thieves don't want to steal your data, since they could easily pull your hard drive if they do. I highly recommend getting an encrypted cloud backup system also. I sleep so much better since I backed up everything important to JungleDisk/Amazon S3.
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