Roster disruption is as you know, subjective. Some people experience little disruption, and others seem to have it all the time.
The disruption that I think most are referring to are the constant changes to duties, anything from an early changing to a late to whole weeks changing after the rosters are published. The main gripe is contactable duties being rostered at inappropriate times (like, for example on day 6 of a run of duties - clearly, if it were intended as a contactable, it would be pointless, as you be into days off by the time they could use you.), but what will often happen, is a couple of days before said contactable, it'll change to a standby, and then often a flight.
The rostering in general is poor - regular earlies to lates (eg, 2-3 earlies followed by 2-3 lates with no days between) - similar story the other way round, usually with a stby in-between. Many fatigue reports on the issue, but no noticeable change in this pattern.
There is no roster agreement, only a policy - with plenty of clauses like "subject to operation needs", "when operationally possible" etc.
There are no bid systems, or preferences, so you can't bid for lates or earlies - roster swaps can be difficult to achieve.
Weekends off - well, it's pot luck. If you play the RDO game consistently, you'll get some weekends off, but if you forget or whatever, there are no guarantees of a weekend off. I think there used to be a policy of 1 weekend off per month, but my roster says differently. No weekends off this month.
Days off are fixed, they don't change these, but you can expect to be contacted on a day off to see if you'll work when they're short.
The winter however is blissfully quiet - although I'd expect to see some changes in the coming years - new aircraft, whilst a welcome development, undoubtedly mean a greater winter schedule (not a bad thing), and probably the loss of the "friendly flight times" slogan - deep nights ala Thompson I'd imagine.
Overall, it's not a bad place to work. There are pro's and con's. Think will need to improve though, as leaky buckets aren't sustainable - you can only shovel sand so quickly, eventually the bucket will empty.
The grass is rarely greener, more a different shade of brown.