Importance of Hadith ...

Those people who think that the Quran is the only source of Islamic Law should read the following verses from the Holy Quran and do a bit of introspection (a mighty bit, that is):

لَقَدْ كَانَ لَكُمْ فِي رَسُولِ اللَّهِ أُسْوَةٌ حَسَنَةٌ لِّمَن كَانَ يَرْجُو اللَّهَ وَالْيَوْمَ الْآخِرَ وَذَكَرَ اللَّهَ كَثِيراً
Indeed in the Messenger of God (Muhammad) you have a beautiful example to follow for him who hopes in (the Meeting with) God and the Last Day and remembers God much. (33:21)

وَإِنَّكَ لَعَلى خُلُقٍ عَظِيمٍ
And verily, you (O Muhammad) are on an exalted standard of character. (68:4)

How can one attempt to follow the "gold-standard" character of the Holy Prophet (peace be upon him) without the Hadith literature?

Also:

قُلْ أَطِيعُواْ اللّهَ وَالرَّسُولَ فإِن تَوَلَّوْاْ فَإِنَّ اللّهَ لاَ يُحِبُّ الْكَافِرِينَ
Say (O Muhammad): "Obey Allah and the Messenger (Muhammad)." But if they turn away, then Allah does not like the disbelievers. (3:32)

وَأَطِيعُواْ اللّهَ وَالرَّسُولَ لَعَلَّكُمْ تُرْحَمُونَ
And obey Allah and the Messenger (Muhammad) that you may obtain mercy. (3:132)

يَا أَيُّهَا الَّذِينَ آمَنُواْ أَطِيعُواْ اللّهَ وَأَطِيعُواْ الرَّسُولَ وَأُوْلِي الأَمْرِ مِنكُمْ فَإِن تَنَازَعْتُمْ فِي شَيْءٍ فَرُدُّوهُ إِلَى اللّهِ وَالرَّسُولِ إِن كُنتُمْ تُؤْمِنُونَ بِاللّهِ وَالْيَوْمِ الآخِرِ ذَلِكَ خَيْرٌ وَأَحْسَنُ تَأْوِيلاً
O you who believe! Obey Allah and obey the Messenger (Muhammad), and those of you (Muslims) who are in authority. (And) if you differ in anything amongst yourselves, refer it to Allah and His Messenger, if you believe in Allah and in the Last Day. That is better and more suitable for final determination. (4:59)

وَمَن يُطِعِ اللّهَ وَالرَّسُولَ فَأُوْلَـئِكَ مَعَ الَّذِينَ أَنْعَمَ اللّهُ عَلَيْهِم مِّنَ النَّبِيِّينَ وَالصِّدِّيقِينَ وَالشُّهَدَاء وَالصَّالِحِينَ وَحَسُنَ أُولَـئِكَ رَفِيقًا

And whoso obeys Allah and the Messenger (Muhammad), then they will be in the company of those on whom Allah has bestowed His Grace, of the Prophets, the Siddiqun (those followers of the Prophets who were first and foremost to believe in them, like Abu Bakr as-Siddiq), the martyrs, and the righteous. And how excellent these companions are! (4:69)

How can one obey the Holy Prophet (peace be upon him) without access to the Hadith literature?