The theory is a pain, but it's nowhere near as bad as many make out. It took me just under 6 months from start to finish, and that wasn't just IR, I did doing the CPL exams in the alternate months.
The IR is 7 exams. IFR comms needs absolutely no revision whatsoever and is a joke. Flight Planning requires little or no revision as all the info you need is there in the exam in the form of CAPs and your route manual. Essentially effort is only required for 5 exams. Most of it is drivel that is absolutely no use in the context of safely operating an aeroplane but some of it, particularly Met, is useful learning.
The main irritation for me was the fact that you have to go to Gatwick for them. This means adding return flights and a hotel into the deal. Plus the CAA exam department are atrocious at sending out paperwork on time, then take weeks to send out the results to candidates. Considering the cost is north of £60 per exam, I really think we deserve better in the 21st century.